This invention relates to a method and apparatus for the rolling of metal wire or rod into a wide, flat metal strip having a width at least 2.5 times the original diameter D of the wire or rod which is rolled.
Various metal fabricating and manufacturing operations utilize various widths and lengths of flat metal strips. Many of these metal strips because of their size, length and factors which may relate to the amount of use and the economics of the use, are not manufactured commercially in such sizes but must be cut from larger sheets of the material to the size required. Obtaining the metal strip in this manner by cutting from a wider sheet is both costly and time consuming, particularly where long continuous lengths of such strip are desired. The long strip must be cut from a wide sheet which is coiled and may be difficult to handle because of the width and long lengths of the sheet. Then, the strip must be machined to eliminate the rough edges caused by the slitting operation, when smooth, square or burr-free edges are required.
In order to save continuing repetition of the phrase "wire or rod", the word "wire" as used herein is to be interpreted broadly to include a relatively thick metal wire such as is often called a "rod". As used herein "D" is intended to mean the original diameter of the wire, and "W" is the width of the resultant flat metal strip.
In conventional rolling mill practice it is usually not economical to pass metal wire through the numerous stations of a rolling mill to reduce the cross-sectional area and thus flatten the wire into a metal strip. In a conventional rolling mill the deforming of the metal takes place between an opposed pair of convex rolls in each station causing displacement of the metal to occur mainly longitudinally, i.e. "down the mill", such that the stock becomes progessively lengthened. Only a relatively minor amount of lateral deformation or widening occurs. Thus, the metal at each successive station, and consequently, the rolls in each successive station must be driven at a faster peripheral speed to match the travelling stock. Moreover, in conventional rolling mill practice the width of a strip produced by rolling a metal wire is usually less than 1.5 D. The great investment needed in such multiple-station rolling mill equipment and in the necessary complex drive mechanism is not justified for the rolling of wire into strip of width less than 1.5 D. Consequently, metal strip is usually slit from wide sheet stock as discussed above.
Where there is demand for a flat strip having superior characteristics such as: (1) closer thickness and width tolerances, (2) improved edge shape, (3) reduced strip camber, and (4) smoother surface finish then it is commercially feasible to roll wire into flat strip. The article Wire-Flattening--An Appraisal of Today's Theory and Practice by A. I. Nussbaum of the Rolling Mill Division of Stanat Manufacturing Co. of Long Island City, New York sets forth various formulas relating the width of the resultant strip to the initial diameter of the wire for conventional rolling techniques. These formulas and the text of this article support the conclusion expressed above that conventional rolling mill practices produce a strip having a width less than 1.5 D.
A paper entitled Rolling Flat Non-Ferrous Wire by G. A. Backman was prepared for presentation to the Annual Convention of The Wire Association, Oct 22-25, 1962, at Baltimore, Maryland. This paper mentions one experiment in which a copper wire having a diameter of 0.005 of an inch was rolled between a pair of convex rolls to produce a strip 0.001 of an inch thick and 0.019 of an inch wide. This is a W/D ratio of 3.8. However, the rolls employed had a diameter 800 times larger than the fine copper wire involved. This 800 ratio is far different from conventional practice and is a totally impractical ratio of roll diameter to wire diameter except for extremely fine wire. In the case of wire, say having a diameter of one-quarter of an inch, each roll diameter would become 200 inches, i.e. sixteen and two-thirds feet in diameter, an unwieldy monstrous pair of rolls.